Navegando por Palavras-chave "LEVATOR ANI MUSCLE"

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    ANDROGEN REGULATION OF THE NICOTINIC ACETYLCHOLINE RECEPTOR-IONIC CHANNEL IN A HORMONE-DEPENDENT SKELETAL-MUSCLE
    (Assoc Bras Divulg Cientifica, 1991-01-01) Souccar, Caden [UNIFESP]; Yamamoto, Lucia Akie [UNIFESP]; Goncalo, M. C.; Lapa, Antonio José [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    The trophic influence of testosterone on the nicotinic acetylcholine receptor-ionic channel (AChR) was studied in the levator ani (LA) muscle of adult male rats (120 days) intact (C) or gonadectomized when 90 days old (G). In the indirectly elicited muscle twitch, the LA from G rats was less sensitive to d-tubocurarine (0.1-1-mu-M) than control muscles (IC25: C = 0.30-mu-M, G = 0.46-mu-M). In G rats, the amplitude of neurally evoked endplate currents (EPC) was reduced by 70%, but the EPC time constant was not changed. Maximal junctional binding of [I-125]alpha-bungarotoxin in the LA (C: 72.5 +/- 13.2 amol/endplate) was reduced by 1.8-fold in LA from G rats, with no change of the association rate constant (C: 5.64 +/- 1.29 10(6) M-1 min-1). The results indicate that testosterone deprivation reduces the junctional AChR density in the rat LA without modifying the binding properties of the receptor.
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    EFFLUX OF ACETYLCHOLINE IN DIMORPHIC SKELETAL-MUSCLE FROM CASTRATED MALE-RATS
    (Assoc Bras Divulg Cientifica, 1991-01-01) Lima-Landman, Maria Teresa Riggio de [UNIFESP]; Goncalo, M. C.; Lapa, Antonio José [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    The effect of testosterone on motor neurons of dimorphic muscles is demonstrable by the increased frequency of miniature end-plate potentials (mepp) and decreased end-plate acetylcholinesterase activity observed in castrated rats. No change occurs in induced acetylcholine (ACh) release. Although these muscles atrophy after castration there is no loss of muscle fibers. In the present study we reinvestigate the neuromuscular transmission in levator ani (LA) muscles from normal (N) adult (120 days) male rats and from rats castrated (C) 30 days before. The measurement of radioactive [H-3]-choline was used to evaluate ACh release since it permits simultaneous estimation of quantal and non-quantal ACh release. The LA muscle was incubated with [H-3]-choline (1-mu-Ci/ml) for 30 min and ACh efflux was measured after washout. The basal release of [H-3]-choline (dpm total tissue radioactivity-1 number of fibers-1) was 296 +/- 33 and 156 +/- 24 in N and C, respectively. Induced ACh release (25 Hz, 5 min) was the same in N and C (653.19 +/- 66.46 and 496.62 +/- 68.67, respectively). These results indicate that castration increased mepp frequency but reduced the total spontaneous release of ACh.
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    PREJUNCTIONAL REGULATORY ACTIONS of ANDROGENS ON A HORMONE-SENSITIVE MUSCLE
    (Wiley-Blackwell, 1994-08-01) Yamamoto, L. A.; Lapa, A. J.; Souccar, C.; Universidade Federal de São Paulo (UNIFESP)
    The influence of androgens and time course of effects induced by hormone deprivation were examined on the spontaneous transmitter release in the levator ani (LA) muscle of 30-180-day-old male rats. the resting membrane potential (RMP) and miniature endplate potentials (mepps) were recorded intracellularly from LA muscle fibers of intact animals or gonadectomized at different ages. in intact animals, the frequency of mepps increased proportionately to the muscle fiber growth up to 60 days, stabilizing thereafter. Gonadectomy at any age did not affect the RMP, but increased the frequency of mepps by 65% to 140%. the effect was detected after 15 days and was unrelated to the degree of muscle atrophy. Independently of the age of gonadectomy control values of mepp frequency were restored after 90 days, while the accompanying postjunctional changes persisted. These results indicate that androgens exert a prejunctional inhibitory influence on the spontaneous transmitter release in the rat LA muscle. the transient nature of the prejunctional effect induced by hormone deprivation indicates an adjustment of nerve terminals to persistent postjunctional alterations. (C) 1994 John Wiley & Sons, Inc.
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    TESTOSTERONE CONTROL of END-PLATE and NON-END-PLATE ACETYLCHOLINESTERASE in the RAT LEVATOR ANI MUSCLE
    (Plenum Publ Corp, 1994-06-01) Godinho, R. O.; Souccar, C.; Lapa, A. J.; Universidade Federal de São Paulo (UNIFESP)
    The time course of effects of castration (5-60 days) and testosterone treatment (15-60 days) of adult male rats were examined on the endplate (+EP) and non-endplate (-EP) acetylcholinesterase (AChE) of the androgen-dependent levator ani (LA) muscle. the thiocholine method was used to determine the enzyme activity. Castration caused LA muscle atrophy within 5 days but reduced the -EP and +EP AChE after 10 and 20 days, respectively. Following 30 days castration -EP and +EP AChE reached respectively 41% and 35% of control activity. Testosterone retrieval restored the control values of both muscle weight and total AChE after 15 and 60 days, respectively. Recovery of the +EP AChE preceded that of -EP AChE by 30 days. the results showed that in the rat LA muscle, +EP and -EP AChE depend on a continuous testosterone regulation that predominates at +EP region spreading thereafter to -EP region. Those data suggest a hormone regulation of AChE exerted indirectly through the synthesis and release of neurotrophic substances.